#include <stdio.h>
#include <stdlib.h>
#include <xcb/render.h>

#define WINDOW_WIDTH 30
#define WINDOW_HEIGHT 30
#define GLYPH_WIDTH 20
#define GLYPH_HEIGHT 20

static const uint32_t glyph_index = 42;

static xcb_connection_t *c;
static xcb_screen_t *screen;
static xcb_visualtype_t *visual;
static xcb_render_pictformat_t pict_format_default;
static xcb_render_pictformat_t pict_format_a8;
static xcb_render_glyphset_t glyphset;
static xcb_window_t window;
static xcb_render_picture_t picture;
static xcb_render_picture_t solid_white_source;

static xcb_visualtype_t *find_visual(xcb_visualid_t visual)
{
	xcb_depth_iterator_t depth_iter = xcb_screen_allowed_depths_iterator(screen);
	xcb_visualtype_iterator_t visual_iter;

	for (; depth_iter.rem; xcb_depth_next(&depth_iter))
		for (visual_iter = xcb_depth_visuals_iterator(depth_iter.data); visual_iter.rem; xcb_visualtype_next(&visual_iter))
			if (visual == visual_iter.data->visual_id)
				return visual_iter.data;
	puts("Couldn't find default visual");
	return NULL;
}

static xcb_render_pictformat_t find_format_for_visual(xcb_render_query_pict_formats_reply_t *formats, xcb_visualid_t visual)
{
	xcb_render_pictscreen_iterator_t screens;
	xcb_render_pictdepth_iterator_t depths;
	xcb_render_pictvisual_iterator_t visuals;
	for (screens = xcb_render_query_pict_formats_screens_iterator (formats);
			screens.rem;
			xcb_render_pictscreen_next (&screens))
	{
		for (depths = xcb_render_pictscreen_depths_iterator (screens.data);
				depths.rem;
				xcb_render_pictdepth_next (&depths))
		{
			for (visuals = xcb_render_pictdepth_visuals_iterator (depths.data);
					visuals.rem;
					xcb_render_pictvisual_next (&visuals))
			{
				if (visuals.data->visual == visual) {
					xcb_render_pictformat_t format = visuals.data->format;
					return format;
				}
			}
		}
	}

	puts("Couldn't find PictFormat for visual");
	return XCB_NONE;
}

static xcb_render_pictformat_t find_format_a8(xcb_render_query_pict_formats_reply_t *formats)
{
	xcb_render_pictforminfo_iterator_t i;

	for (i = xcb_render_query_pict_formats_formats_iterator(formats); i.rem; xcb_render_pictforminfo_next(&i)) {
		if (i.data->type != XCB_RENDER_PICT_TYPE_DIRECT)
			continue;
		if (i.data->direct.red_mask != 0)
			continue;
		if (i.data->direct.green_mask != 0)
			continue;
		if (i.data->direct.blue_mask != 0)
			continue;
		if (i.data->direct.alpha_mask != 0xff)
			continue;
		return i.data->id;
	}

	puts("Couldn't find A8 PictFormat");
	return XCB_NONE;
}

static void redraw()
{
	xcb_rectangle_t rect;
	xcb_render_color_t color;
	uint8_t glyph_commands[] = {
		/* len */
		1,
		/* Padding */
		0, 0, 0,
		/* x and y shift (16bit) */
		5, 0, 5, 0,
		/* Glyph */
		42,
		/* Padding */
		0, 0, 0
	};

	rect.x = 0;
	rect.y = 0;
	rect.width = WINDOW_WIDTH;
	rect.height = WINDOW_HEIGHT;

	color.red = 0xffff;
	color.green = 0xffff;
	color.blue = 0;

	xcb_render_fill_rectangles(c, XCB_RENDER_PICT_OP_SRC, picture, color, 1, &rect);
	xcb_render_composite_glyphs_8(c, XCB_RENDER_PICT_OP_OUT_REVERSE, solid_white_source,
			picture, XCB_NONE, glyphset, 0, 0, sizeof(glyph_commands), glyph_commands);
}

int main()
{
	xcb_render_query_pict_formats_reply_t *formats;
	xcb_render_glyphinfo_t glyph_info;
	uint8_t *glyph_data;
	size_t glyph_data_length;

	if (GLYPH_WIDTH % 4 != 0)
		puts("Bad glyph width");
	glyph_data_length = GLYPH_WIDTH * GLYPH_HEIGHT;
	glyph_data = malloc(glyph_data_length);
	for (int y = 0; y < GLYPH_HEIGHT; y++)
		for (int x = 0; x < GLYPH_WIDTH; x++) {
			uint8_t data = 0x7f;
			switch ((x % 2) + (y % 2)) {
			case 0:
				data = 0;
				break;
			case 1:
				data = 0xff;
				break;
			}
			glyph_data[y * GLYPH_WIDTH + x] = data;
		}

	glyph_info.width = GLYPH_WIDTH;
	glyph_info.height = GLYPH_WIDTH;
	glyph_info.x = 0;
	glyph_info.y = 0;
	glyph_info.x_off = 42;
	glyph_info.y_off = 21;

	c = xcb_connect(NULL, NULL);
	if (xcb_connection_has_error(c))
		puts("Couldn't connect");

	screen = xcb_setup_roots_iterator(xcb_get_setup(c)).data;
	visual = find_visual(screen->root_visual);
	formats = xcb_render_query_pict_formats_reply(c, xcb_render_query_pict_formats(c), NULL);
	pict_format_default = find_format_for_visual(formats, screen->root_visual);
	pict_format_a8 = find_format_a8(formats);
	free(formats);

	window = xcb_generate_id(c);
	xcb_create_window(c, screen->root_depth, window, screen->root,
			10, 10, WINDOW_WIDTH, WINDOW_HEIGHT, 0,
			XCB_COPY_FROM_PARENT,
			visual->visual_id,
			XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK,
			(const uint32_t[]) { 1, XCB_EVENT_MASK_EXPOSURE });
	picture = xcb_generate_id(c);
	xcb_render_create_picture(c, picture, window, pict_format_default,
			XCB_RENDER_CP_POLY_MODE,
			(const uint32_t[]) { XCB_RENDER_POLY_MODE_IMPRECISE });
	glyphset = xcb_generate_id(c);
	xcb_render_create_glyph_set(c, glyphset, pict_format_a8);
	xcb_render_add_glyphs(c, glyphset, 1, &glyph_index, &glyph_info,
			glyph_data_length, glyph_data);
	solid_white_source = xcb_generate_id(c);
	xcb_render_create_solid_fill(c, solid_white_source, (xcb_render_color_t) { 0xffff, 0xffff, 0xffff, 0xffff });
	xcb_map_window(c, window);

	xcb_flush(c);
	while (!xcb_connection_has_error(c)) {
		xcb_generic_event_t *ev = xcb_wait_for_event(c);
		switch (ev->response_type) {
		case XCB_EXPOSE:
			redraw();
			break;
		default:
			printf("Unknown event of type %d\n", ev->response_type);
			break;
		}
		free(ev);
		xcb_flush(c);
	}

	xcb_disconnect(c);
	return 0;
}